Environmental system including an electro-osmotic element for an immersion lithography apparatus

Abstract

An environmental system that controls an environment in a gap between an optical assembly and a device includes a fluid barrier, an immersion fluid system, an electro-osmotic element, and a control system. The fluid barrier is positioned near the device and maintains the electro-osmotic element near the gap. The immersion fluid system delivers an immersion fluid that fills the gap. The control system applies an electrical voltage to the electro-osmotic element that causes the electro-osmotic element to transport at least a portion of the immersion fluid that is near the fluid barrier and the device away from the device. The electro-osmotic element can be made of a porous material.

1 . A lithography apparatus, comprising: 
 a stage that supports a work piece;    an optical assembly that projects an image onto the work piece on the stage;    a gap between the optical assembly and the work piece, the gap filled with an immersion fluid; and    an electrokinetic sponge positioned adjacent to the gap, the electrokinetic sponge transports immersion fluid that has exited the gap away from the gap.    
   
   
       2 . The lithography apparatus of  claim 1 , wherein the electrokinetic sponge substantially surrounds the gap between the optical assembly and the work piece.  
   
   
       3 . The lithography apparatus of  claim 1 , further comprising a control system that controls the transport of immersion fluid through the electrokinetic sponge.  
   
   
       4 . The lithography apparatus of  claim 1 , wherein the electrokinetic sponge includes a plurality element segments that cooperate to substantially surround the gap between the optical assembly and the work piece.  
   
   
       5 . An environmental system for maintaining a gap full of an immersion fluid, the gap being formed between an optical assembly and a device, the environmental system comprising: 
 an electro-osmotic element that is positioned near the device; and    a control system that applies a voltage across the electro-osmotic element that causes the immersion fluid to move through the electro-osmotic element.    
   
   
       6 . The environmental system of  claim 5 , further comprising a fluid barrier that substantially encircles the gap, the fluid barrier maintaining the electro-osmotic element near the gap, and wherein the electro-osmotic element substantially encircles the gap.  
   
   
       7 . The environmental system of  claim 5 , wherein the electro-osmotic element includes a plurality of pores.  
   
   
       8 . The environmental system of  claim 5 , wherein the electro-osmotic element has a pore size in the micron range.  
   
   
       9 . The environmental system of  claim 5 , further comprising an immersion fluid source that delivers the immersion fluid to the gap.  
   
   
       10 . The environmental system of  claim 5 , wherein the control system applies a voltage of at least approximately five volts to the electro-osmotic element.  
   
   
       11 . The environmental system of  claim 5 , wherein the electro-osmotic element includes a first surface and an opposite second surface that is positioned near the device and wherein the control system applies a voltage between the first and second surfaces of the electro-osmotic element.  
   
   
       12 . The environmental system of  claim 11 , wherein the polarity of the voltage causes the immersion fluid to flow from the second surface to the first surface.  
   
   
       13 . The environmental system of  claim 11 , wherein the polarity of the voltage causes the immersion fluid to flow from the first surface to the second surface.  
   
   
       14 . The environmental system of  claim 5 , wherein the electro-osmotic element includes a first element segment, a second element segment and an insulator that separates the element segments.  
   
   
       15 . The environmental system of  claim 14 , wherein the control system applies a first voltage to the first element segment and a second voltage to the second element segment, the first voltage being different than the second voltage.  
   
   
       16 . The environmental system of  claim 5 , further comprising (i) a fluid barrier that cooperates with the electro-osmotic element to form a removal chamber adjacent to the electro-osmotic element, and (ii) an immersion fluid source that directs an immersion fluid into the removal chamber.  
   
   
       17 . An exposure apparatus for transferring an image to a device, the exposure apparatus comprising: an optical assembly, a device stage that retains the device, and the environmental system of  claim 5  that controls an environment in a gap between the optical assembly and the device.  
   
   
       18 . An environmental system for maintaining a gap full of immersion fluid, the gap being formed between an optical assembly and a work piece, the environmental system comprising: 
 an electro-osmotic pump positioned near the work piece that captures immersion fluid that exits the gap.    
   
   
       19 . The environmental system of  claim 18 , wherein the electro-osmotic pump includes an electro-osmotic element positioned near the work piece and a control system that applies a voltage across the electro-osmotic element that causes the immersion fluid to move through the electro-osmotic element.  
   
   
       20 . The environmental system of  claim 19 , further comprising a fluid barrier that substantially encircles the gap, the fluid barrier maintaining the electro-osmotic element near the gap, and wherein the electro-osmotic element substantially encircles the gap.  
   
   
       21 . The environmental system of  claim 19 , wherein the electro-osmotic element including a plurality of pores.  
   
   
       22 . The environmental system of  claim 19 , further comprising an immersion fluid source that delivers the immersion fluid to the gap.  
   
   
       23 . The environmental system of  claim 19 , wherein the electro-osmotic element includes a first surface and an opposite second surface that is positioned near the work piece and wherein the control system applies a voltage between the first and second surfaces of the electro-osmotic element.  
   
   
       24 . The environmental system of  claim 23 , wherein the polarity of the voltage causes the immersion fluid to flow from the second surface to the first surface.  
   
   
       25 . The environmental system of  claim 23 , wherein the polarity of the voltage causes the immersion fluid to flow from the first surface to the second surface.  
   
   
       26 . The environmental system of  claim 19 , wherein the electro-osmotic element includes a first element segment, a second element segment and an insulator that separates the element segments.  
   
   
       27 . The environmental system of  claim 26 , wherein the control system applies a first voltage to the first element segment and a second voltage to the second element segment, the first voltage being different than the second voltage.  
   
   
       28 . A method for transferring an image to a work piece, the method comprising the steps of: 
 supporting the work piece with a stage;    providing an optical assembly that projects the image onto the work piece, the optical assembly being separated from the work piece by a gap;    filling the gap with an immersion fluid; and    transporting immersion fluid that has exited the gap with an electrokinetic sponge.    
   
   
       29 . The method of  claim 28 , further comprising the step of encircling the gap with a fluid barrier, the fluid barrier maintaining the electrokinetic sponge near the gap, and wherein the electrokinetic sponge substantially encircles the gap.  
   
   
       30 . The method of  claim 28 , further comprising the step of applying a voltage across the electrokinetic sponge with a control system that causes the immersion fluid to move through the electrokinetic sponge.  
   
   
       31 . The method of  claim 28 , wherein the electrokinetic sponge includes a first surface and an opposite second surface that is positioned near the device and wherein the control system applies a voltage between the first and second surfaces of the electrokinetic sponge that causes immersion fluid to flow between the surfaces.  
   
   
       32 . A method for making an exposure apparatus for transferring an image to a device, the method comprising the steps of providing an optical assembly, and controlling the environment in the gap by the method of  claim 28.